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New physics in the weak interaction of $\bar B\to D^{(*)}τ\barν$

Recent experimental results on exclusive semi-tauonic B meson decays, B -> D(*) tau nu, showing sizable deviations from the standard model prediction, suggest a new physics in which the structure of the relevant weak charged interaction may differ from that of the standard model. We study the exclusive semi-tauonic B decays in a model-independent manner using the most general set of four-Fermi interactions in order to clarify possible structures of the charged current in new physics. It turns out that correlations among observables including tau and D* polarizations and q^2 distributions are useful to distinguish possible new physics operators. Further, we investigate some interesting models to exhibit the advantage of our model-independent analysis. As a result, we find that two Higgs doublet models without tree-level FCNC and the minimal supersymmetric standard model with R-parity violation are unlikely to explain the present experimental data, while two Higgs doublet models with FCNC and a leptoquark model are consistent with the data.